The present invention generally relates to boiler cleaning and more particularly to cleaning the surfaces of heat exchange tubes in large scale industrial boilers by the application of high frequency shock energy.
It is well known that during operation of boilers, various combustion by-products become deposited on the boiler tubes and other heat transfer surfaces located within the boiler. These by-products accumulate as hardened encrustations of soot, slag, ash and scale. Unless frequently and thoroughly removed, the deposits cause significant heat loss and seriously impair the efficiency of the boiler. As modern boiler operating temperatures have increased and the use of lower quality fuels have become more commonplace, it has become increasingly difficult to remove the encrustations.
Various techniques have been utilized to remove the deposits from the surfaces of the boiler tubes. By way of illustration, these techniques include manual and automated sootblowers; manual scraping of the tube surfaces; and manual and automated use of air hammers to vibrate the tubes. Of these techniques, none have been found to be completely satisfactory and each has been found to have limitations and disadvantages.
One disadvantage of the vibrational type of cleaning systems, generally known as rappers, is that the systems require prior and relatively precise knowledge of the spacing between the individual tubes of the tube banks or bundles in the boiler. These known vibrational cleaning systems typically do not lend themselves to retrofitting applications and lack a large degree of field adjustability to accommodate for the existing variances in tube spacing.
With the above and other limitations in mind, it is an object of the present invention to provide an improved apparatus for cleaning surfaces of the heat exchange tubes in large scale industrial boilers. In achieving the above, the invention provides an apparatus which dislodges encrustations that have accumulated on the boiler tubes by the application of high frequency shock energy.
An additional object of this invention is to provide an apparatus which is readily retrofitted into existing boilers and which can accommodate a wide range of variations in boiler tube spacing. As such, the present invention is field adjustable.
These and other objects of the invention are obtained by providing an apparatus which generally comprises a vibrator for producing high frequency shock energy, a tie bar extending transversely of a row of heat exchange tubes, and a plurality of tube plates which extend generally transversely of both the tie bar and heat exchange tubes. During operation, high frequency shock energy is transmitted from the vibrator through both the tie bar and the tube plates to the heat exchange tubes causing the accumulated deposits to be dislodged.
According to one embodiment of the invention, the apparatus is adapted for cleaning generally horizontal heat exchange tubes which are mounted in parallel horizontal rows within the boiler. In this embodiment, the tie bar extends generally transversely of the length of the tubes and is positioned between vertically adjacent rows of the tubes. The tube plates are rigidly mounted to the tie bar adjacent to at least two tubes, one on each side of the tie bar and are also grouped in pairs so as to have the tubes positioned therebetween. At least one of the tube plates includes a tab or tube stop that extends between the vertically adjacent tubes along side of the tie bar. The tube stop prevents rotation of the entire assembly about the longitudinal axis of the tie bar. The vibrator is mounted externally of the boiler and is positioned to axially coincide with the tie bar. As an end of the tie bar is struck by a portion of the vibrator, high frequency shock energy is transmitted to the tubes causing dislodgement of the deposits.
In a second embodiment of the invention, the heat exchange tubes are vertically mounted. As in the prior embodiment, the tie bar extends generally transverse to the longitudinal (vertical) axis of the tubes and is positioned adjacent to at least one row of the tubes. The tube plates are again provided in pairs with each pair being arranged on opposing sides of a row of heat exchange tubes. The tube plates are mounted transverse to both the heat exchange tubes and the tie bar. Each pair of tube plates is rigidly attached to a row of the heat exchange tubes and welded to the tie bar so that high frequency shock energy is transmitted from the vibrator, through the tie bar and the tube plates, to the rows of the heat exchange tubes.
In each of the embodiments, the tie bar is mounted transversely to the longitudinal axis of the tubes and the tube plates are mounted transversely to the longitudinal axis of both the tie bar and the tubes. Because a multiple number of pairs are used and each pair of tube plates extends along an individual row of tubes, a multiple number of rows of the heat exchange tubes are cleaned by the transmission of the high frequency shock energy from a single vibrator.
The embodiments also enjoy increased flexibility since the tube plates are individually fitted onto the tie bar to compensate for individual tube spacing variations. Additionally, neither embodiment requires welding of the apparatus directly to the surfaces of the heat exchange tube. Because of the above advantages, the present invention can be used on existing tube banks, which may have uneven tube spacing, without requiring prior or precise knowledge of the actual tube spacing.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims taken in conjunction with the accompanying drawing.